Plants have been used as a source of medicine for the treatment of different diseases from thousands of years ago. There is numerous evidences are available for use of plants as a medicine in the treatment of diseases in Indian, Egyptian, Chinese, Greek and Roman system of medicine. Pharmacognosy is the study of medicines derived from natural sources, mainly from plants which may further lead to development of new drug. The exploration, extraction and screening of biological diversity such as herbs, spices, microbes and other natural resources is the worldwide activity in recent years. Phytochemicals are the naturally available bioactive compounds which are derived from different plant parts and are primarily responsible for biological activities. The most important chemical compounds which are present in the plants are alkaloids, phenols, saponins, carbohydrates, terpenoids, steroids, flavonoids and tannins etc.
- Medicinal plants
- biological activities
Since from ancient period man depended on nature for their survival and lives strictly connected with nature. Man depends upon surrounding environment for their livelihood, healthcare, and sustenance and also for basic needs (food, fibers, shelter, clothing and gum). Besides providing basic necessities, plants also provided his requirement of medicine. Along with the plant man has been started using animal products and other bio-resources available in nature for preparation of medicine. As a result, different traditional medicine systems have evolved based on environmental condition, social and cultural background with respect to the ethnic group in different countries [1, 2].
Plants are served as major natural resources for traditional as well as modern medicinal system all over the world. The therapeutic potential of plants and plant products can be traced back to thousands of years ago. The information with respect to medicinal benefits of plants with other therapies has been preserved in several documentations in Babylonia, Egypt, China, Greece and Rome etc. Previous works of Theophrastus (370–287 B.C.), Aristotle (384–322 B.C.), Hippocrates (460–370 B.C.) and Dioscorides (50–100 A.D) are providing evidence that Greeks and Romans are familiar with many of today’s plant drugs. The “Ebers Papyrus”, the best known Egyptian pharmaceutical record documented over 700 drugs represents the history of Egyptian medicine (1500 BC). Erh-ya (300B.C), Svu-ching (1000B.C) and Ben-tsao (1250A.D) are the early herbal documentations available in China, describes more than 600 medicinal plants . In Asia, the earliest records of plants usage are found in the clay tablets in Mesapotamia (1700 BC). In India, herbal remedies and health care preparations are also described in ancient texts like ‘Charka Samhita’ (100–800 B.C), ‘Sushruta Samhita’ (800–700 B.C), ‘Rigveda’ (1400–1800 B.C) and ‘Atharva-veda’ (4500–2500 B.C). Ayurveda is the fundamental source of Vedic knowledge for understanding remedial properties of plants (1000 BC). Ayurveda is considered as ancient medicinal system and it is the compilation of ‘Charka Samhita’, ‘Sushruta Samhita’ and ‘Ashtanga Hridaya Samhita’ . In addition to Ayurveda, Siddha and Unani are other conventional systems of medicine providing additional information of plant based drugs used in India. ‘Unani’ system of medicine originated in Greece and introduced to India by Arabs and Persians after the discovery of sea route to India. During 10th to 15th century, ‘Sidda’ system of medicine originated in southern parts of India and is parallel to Ayurvedic system of medicine (Figure 1) .
Now a day the herbal medicine has renewed attention and hopeful both practical and scientific view points. Herbal remedies are complex mixture different parts of single herb or many herbs which may sometime produce synergistic effect with each other ensuing in the increased therapeutic potential of drug. The identification of biologically active compound responsible for its medicinal property and there is a crucial requirement for quality control. So the correct identification and quality assessment is important to ensure quality of herbal medicine, which contributes to its safety and efficacy. Therapeutic action of herbal formulation depends on its photochemical constituents. The photochemical investigation of the medicinally important plants should be carried out, as this would be beneficial in standardization, quality assessment and efficacy of herbal drugs. Thus pharmacognosy is considered as important tool to study medicinal plants for their identification, validation and standardization [6, 7].
2. Bioprospecting of medicinal plants
Biodiversity prospecting or bioprospecting of the medicinal plants is the worldwide activity in the current years. Biodiversity prospecting is the exploration, extraction and screening of biological diversity and indigenous knowledge for commercially valuable genetic and biochemical resources. In early stages, bioprospecting mainly focused on the plants from the forest ecosystem. But in recent years, various other forms of biodiversity such as insects, algae and microorganisms have been explored with substantial success . During recent years this activity involves the use of advanced technologies to develop new pharmaceuticals, agrochemicals, cosmetics and other bi-products from biological diversity . With the help of advanced technology and sophisticated techniques and tools it has become effective way to conduct research on metabolic response of living system, genetic manipulation and novel drug discovery through bioprospecting. Various bio-active molecules have been isolated and tested for their pharmacological activities .
3. Pharmocognosy of medicinal plants
The term pharmocognosy was first time coined by the Austrian physician Schmidt in 1811. A “crude drug” means a dried unprepared natural material of plant, animal or mineral origin, which is used for medicine. The word pharmacognosy is derived from the Greek word
During pharmacognostic investigations, physico-chemical analysis also considered as important parameter in evaluation and identification of crude drug. Macroscopic and microscopic analysis is necessary for the detection of adulterants, contaminants of herbal drug and for assessing quality before going for further study. The extractive value and solubility value is useful to evaluate specific chemical constituent dry yield in different solvents. Ash value analysis is useful in determination of unrelated matter (sand and soil) adhering to the surface of plant . Moisture content is essential for evaluation of stability of crude drug. Fluorescence analysis is a reliable tool for standardization of crude drug. The different chemical constituent present in the plant extract showed characteristic fluorescence when illuminated suitably. Certain chemical substances that are not naturally fluorescence themselves are treated with different reagent to attain fluorescence .
4. Phytochemicals of medicinal plants
The curative properties of medicinal plants are due to presence of major group of active components which are mainly alkaloids, triterpenoids, essential oils and phenolic compounds etc. Alkaloids are the secondary metabolites of plants having noticeable pharmacological activity. Roots, leaves, bark and seeds are common parts of plants which contain alkaliods. In general the alkaloids occur as salts of citric acid, oxalic acid, acetic acid and tartaric acid. These are mostly colorless, water insoluble and non-polar solvents soluble in nature. Pharmacologically, alkaloids act as cardiac depressants, antihypertensive, anti-leukemic, analgesic, nerve stimulants and local anesthetic. Triterpenoids are made up of six isoprene units. Saponins, sterols and cardiac glycosides are chief triterpenes. The medicinal plants which have saponins are roots of
5. Biological activity of medicinal plants
Due to the presence of bioactive molecules plants are used as phytomedicine to cure many complaints.
More than 35,000 plant species have been investigated and resulted in the discovery of anticancer drugs such as ‘Vincristine’, ‘Vinblastine’, ‘Taxol’, ‘Etoposide analogs’, ‘Camptothecin’ etc. Many number of effective drugs derived from higher plants were alkaloid ‘Paclitaxol’, isolated from
A wide range of reports are available on phytochemicals and pharmacological activity of medicinal plants. Several workers have reported biological activity of medicinal plants. Pharmacognostic and preliminary phytochemical analysis of
In parallel, phytochemical screening of
Antimicrobial activity of different extract of
The in vitro cytotoxic activity of
6. Current status of herbal medicine
World Health Organization estimated that 80% of the populations of developing countries still depend on plant drugs for their primary health care needs. According to survey of World Health Organization, the practitioners of traditional medicinal system treat about 8% of patients of India, 85% in Burma and 90% in Bangladesh. India comprises of 2.4% of the total geographical area of the world. The country accounts for an average of 8% of the total global biodiversity with approximately 49,000 species of plants of which 4,900 are endemic . Approximately 2,65,000 species of seed plants exists on earth and less than half of these have been studied systematically for their chemical composition and medicinal value .
Greater part of drugs now available in the market is simple semi-synthetic derived from naturally occurring substances. Up to 50% the approved herbal drugs used today are from either directly or indirectly synthesized from natural products including plants, microorganisms, fungi and animals. According to an estimate, about 25% of the world pharmaceutical products find a significant degree of origin in indigenous communities, which represents more than a 2000 billion dollar share market .
In many developed countries, the percentage of the population which has used herbal medicines at least once is 48% in Australia, 70% in Canada, 42% in USA, 38% in Belgium and 75% in France. Malaysia, spent US$ 500 million annually on herbal health care, compared to about US$ 300 million on allopathic medicine. In USA, annual spending on conventional medicines was estimated at US$ 2700 million. In Australia, Canada and the United Kingdom, annual expenditure for herbal medicine is estimated US$ 80 million, US$ 2400 million and US$ 2300 million respectively. In several parts of the world, outflow on herbal medicinal products is not only significant, but also growing rapidly .
The allopathic medicine has side effects and hazardous to human beings. After realizing toxicity and adverse effects of allopathic medicines, a shift in universal trend from synthetic to herbal medicines has been observed both in developed and developing countries . The most important facts about herbal medicine are that these medicines have no side effect and available in low of cost. Therefore high dose of herbal medicine or wrong medicine consumed by patient mistakenly does not cause any adverse effect on the body.
7. Conservation of medicinal plants
Medicinal plants are the basic raw materials of pharmaceutical industries and is highly depends on medicinal plant for extraction of medicinally important compounds. During this time with the advancement of science and technology, over growing demand of pharmaceutical industries, the useful medicinal plants were over exploited by the men. So there is a need of conservation and propagation of valuable, rare and endangered medicinal plants by using advanced biotechnology methods .
Plants occupy a major sector of health care system and represent a most important natural resource. Therefore conservation of species is most effectively achieved through the management of the wild population and natural habitats. In most of cases medicinal plants either do not produce seeds or too small seeds. In order to overcome these barriers
Recently in India, several institutes and organizations involved in different aspects of drug discovery and conservation medicinal plant from natural resources. Initiative work designed for finding novel bioactive compound from plant, fungi, microbes etc. are set up by Council of Scientific and Industrial Research (CSIR), Central Drug Research Institute (CDRI), Regional Research Laboratory (RRL), Jammu and Kashmir. Golden Triangle Partnership (GTP) in collaboration with Department of Ayush, CSIR and ICMR involved in the validation of traditional ayurvedic medicine for effective drug discovery. During last few decades, the Department of Biotechnology and Government of India has set up two Micropropagation Technology Parks at National Chemical Laboratory (NCL), Pune and Tata Energy Research Institute (TERI), New Delhi .
Since time immemorial plants are utilized as chief source of therapeutic agents. The medicinal plants are not only the source of healthcare but also an important product of world trade. In last few years the trade of medicinal plant is increase rapidly because herbal drugs are easily available at lowest prices and less side effects . The remedial properties of plants due to presence of intricate chemical components with different compositions and biological function.
Herbal medicine is widely practiced in worldwide and is considered to effective and affordable. Recently significant attention has been made to utilize eco-friendly and bio-friendly plant based product for cure of different human diseases . This increases global pharmaceutical demand from last few years. Due to increasing demand of supply of plants as a raw material in pharmaceutical industries, biological diversity of plants is in danger. Therefore there is a need to advance research for the development and characterization of natural drugs with the help of better screening methods from plants and other natural sources. However, medicinal plants often being subjected to scientific validation and for discovery of safe and potential natural drug to fight against diseases [36, 37].
Conflict of interest
The authors declare no conflict of interest.